Electrical deactivation by vacancy-impurity complexes in highly As-doped Si

Abstract

We have applied positron annihilation and Hall-effect/resistivity experiments to identify and quantify vacancy-impurity complexes formed in molecular-beam epitaxially grown Si at very high As doping levels of $>{10}^{20}{\mathrm{cm}}^{\ensuremath{-}3}.$ The results indicate that $\mathrm{V}\ensuremath{-}{\mathrm{As}}_{3}$ is the dominant vacancy defect which exists at concentrations relevant to the electrical deactivation of doping. Larger complexes, tentatively identified as ${\mathrm{V}}_{2}\ensuremath{-}{\mathrm{As}}_{5},$ are also present at high concentrations. The $\mathrm{V}\ensuremath{-}{\mathrm{As}}_{3}$ and ${\mathrm{V}}_{2}\ensuremath{-}{\mathrm{As}}_{5}$ defects are removed by annealings at $800\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ and $900\ifmmode^\circ\else\textdegree\fi{}\mathrm{C},$ respectively. The rapid thermal annealing leads to lowest concentrations of these deactivating defects, indicating that their formation is limited by migration processes during the cooling down.